In recent structural biology, techniques for analyzing the conformation of a protein using NMR or an electron microscope have been developed dramatically. Among them, X-ray crystal structural analysis is the most suitable technique for revealing the conformation at atomic resolution, provided that a high-quality protein crystal is obtained. In the world's largest synchrotron radiation facility, SPring-8, a microfocus beamline has newly begun to operate, in addition to an optimized RIKEN beamline for structural biology. This is making it possible to collect diffraction data of microcrystals, which were difficult to measure heretofore. For example, Japanese Laid-open Patent Publication No. 2007-055931 and Japanese Laid-open Patent Publication No. 2007-230841 disclose methods for crystallizing a protein.
In conventional development of techniques for protein crystallization, large-scale screening of crystallization conditions, micro-dispensation of a sample at the nanoscale, and a protein crystallization apparatus that enables further rapid setup of crystallization have been mainly developed, based on crystallization methods such as a hanging drop method, a sitting drop vapor diffusion method, and an oil microbatch method. As a result, many conformations of proteins have been determined.
However, there is a problem that a high-quality protein crystal is still difficult to obtain even with the conventional techniques.